


Trap of Mind

by MiliusPrime



Category: Fire Emblem, Fire Emblem: Fuukasetsugetsu | Fire Emblem: Three Houses
Genre: Alpha/Beta/Omega Dynamics, Anal Sex, Knotting, M/M, Omega Verse, Pining, Praise Kink, Pre-Relationship, Sexual Fantasy, Smut
Language: English
Status: In-Progress
Published: 2019-09-12
Updated: 2019-10-04
Packaged: 2020-10-17 00:29:38
Rating: Explicit
Warnings: Creator Chose Not To Use Archive Warnings
Chapters: 2
Words: 4,397
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/20611928
Author URL: https://archiveofourown.org/users/MiliusPrime/pseuds/MiliusPrime
Summary: Byleth starts to go into rut mid-training session with his favorite prince, and after hasty retreat lets his mind finish all the things he'd love to have done to him.





	1. Of Mind

Dimitri, the young crown prince of Faerghus, was Byleth’s favorite sparring partner in the entire monastery. More than Bylia, more than Felix, more even than Byleth’s father himself.

Why? Because for once in Byleth’s life, he didn’t have to hold back. He could swing his blade with the full force of his strength without having to fear for the other’s safety, and that in and of itself alone was more cathartic than anything else. Dimitri likewise could use his full brute strength, and so, from a professor’s standpoint, it really was a good thing for them to be sparring partners so often. Dimitri would work up more of a sweat that way, get more out of it.

From a healthy young adult standpoint, it was also really appealing to get first row seats to Dimitri’s face red with exertion, the sweat that glistened on his brow and elegant neck. And to repeatedly snag the young lancer with a grab leading into a pin move. Byleth would never laugh at any of his students (if you could call them that, he always felt more like a tutor than a professor since they were all the same age) but he had to admit he was amused at how Dimitri never expected him to throw him into a pin _ again _, that would be too predictable. But he did, always changing up the movement just a little so that the blond young man would never see it coming. His reward was that he got to press himself bodily against the handsome prince and restrain his arms or perhaps still him with a chokehold.

Felix, ever present at the training grounds these days, must have caught on because he would give him a dirty look and swing his sword harder on the next thrust. Byleth didn’t care - in fact, it just made him want to laugh. He respected Felix a lot for his sharp wit and talent with a blade, but he swore that guy was allergic to fun and relaxation.

“Predicting what your opponent is about to do is half the battle. You can’t rely on their body cues alone - you’ll get tricked that way, like I keep doing with you.” Byleth explained, bringing his sword to parry Dimitri’s thrust. “You have to imagine you are them - they want victory just as much as you do. Whatever you would do in their position, is very likely what they are about to attempt.”

Deflecting a harsh blow off the side of his sword, he steps in to the movement and hits Dimitri’s ankle, pushing him over when he tries to regain his balance - using his lance, very good actually - and knocking Dimitri’s weapon from his grip to straddle his middle. 

“Like that.” He said with a smug smile as Dimitri yielded. The alpha in him relished this position, a fierce surge of pleasure going through his body. He couldn’t deny he enjoyed wrestling the handsome young prince to the ground and holding him there.

“You could simply disarm me without knocking me to the ground, you know.” Dimitri seems a bit miffed, perhaps chagrined by this being the tenth time he’s gotten pinned in the hour. 

“Yeah, but where’s the fun in that?” Byleth was usually only held the position long enough to make a passing remark and clamber off, but something itched within him to go further. “Besides, it’s not my fault you always leave yourself open to it… it’s like you’re calling out to me - Throw me, throw me, pleaaaase~”

Dimitri grunted and rolled his eyes beneath him. “I am aware of your desire to throw things - the heavier, the better, from my observations.”

Byleth rolled off him, yanking him up with a hand that was readily taken, he noted with content.

“Don’t act like you’ve never wanted to just sprint to see how fast you can run, or yell at the top of your lungs just to see how loud you can yell. Besides, throwing heavy things that far comes in handy a lot - people pay good money for people to clear large things out of their way.”

They began again, Dimitri making the first move this time - a feinted thrust and then a sweeping diagonal blow. 

“I shall admit I have had the good fortune to have no need to worry about such expenses,” Dimitri grimaced as he dodged Byleth’s next blow. “If anything, I create new ones with the things I break.”

“I wouldn’t worry about that. It’s not like you do it on purpose. And you’re definitely the kind of person that deserves to be taken care of, regardless.” The blond prince staggered in surprise on his next parry, a small frown on his regal features. 

“What do you mean by that?”

“Oh, I meant no offense of course, you’re a very capable man.” Byleth insisted sheepishly, though there were no openings in his stance - battle was like second nature to him, he didn’t really need to think. “I just meant to say that I can see why you have several loyal people around you who support you.”

At the odd look on Dimitri’s face, Byleth noticed that a growing heat was forming in the pit of his stomach. For the first time in the two hours they’d spent training, he felt the back of his neck break out in a sweat. Well shit. Byleth hoped he wasn’t getting sick. There was nothing he hated more than losing face physically.

Meaning to end the training session swiftly, Byleth hooked his blade around the shaft of Dimitri’s extended lance and tugged forward, knocking him down when he staggered forward, and, as usual, bodily pinning him down so that he could not retrieve his weapon, nor his footing.

Not that Dimitri didn’t try - not one to give up, the young man squirmed underneath him, grasping for his lance nearby.

“Ah-ah.” Byleth chided, grasping the wrist of that hand and pinning it above the prince’s head, the movement causing him to lean forward, chest pressed firmly against Dimitri’s. 

There was that heat again. It churned in the pit of his stomach, and he felt almost light-headed. He shook his head, pressing his eyes closed to banish the feeling. Maybe he hadn’t eaten enough?

He froze at the look on Dimitri’s face when he reopened his eyes. The young prince’s sky blues were hazed over, eyebrows drawn upward, drawing in deep breaths through his open mouth.

“Uh, what-”

“You smell… so _ good _, professor.” 

Byleth raised an eyebrow. “Not that I get sweaty often, but I’m pretty sure I’m sweating now, so that’s kind of an odd thing for you to… say…” He trailed off, feeling something stiffen below him.

Dimitri’s… lance, as it were, poked up at his thigh, and Byleth suddenly completely understood the reason for the look on Dimitri’s face as his stomach blazed with heat.

If he could, he would throw the largest rock ever straight up into the heavens - he was really going into a rut _ now? _ In front of his… best friend, who of _ course _appeared to not be alpha, and also, unfortunately for him, reacting to his mating pheromones.

Byleth immediately released Dimitri’s wrist, scrambling off of him like a hot potato.

“Woah, uh… -yikes, this is really awkward- um, sorry about that Dimitri. Still getting used to my- well, you know.” Byleth drew a hissing breath through his teeth. “God this is so awkward.”

“Anyways, good work with training today, _ I _ am going to… go shower. Don’t be concerned if Bylia substitutes for my class for the next few days aaaand yeah. See you.” With that, Byleth very, very briskly walked away to go take care of the universe’s cruel joke, hoping that Dimitri would somehow forget that whole thing even happened.

Might as well pick up some large rocks on his way. He already felt like crushing something, anything really, and that was without the added hormones that had already swirled into a mantra of “fuck, pound, bite, _ dominate _, claim, impregnate” that Byleth honestly found ridiculous.

\---

Byleth was not having a great time.

Ruts didn’t set on that fast, but once you were fully and truly in one, not having a partner to sate your mating urges with was truly difficult. It was not Byleth’s first rut, but they didn’t seem to get much easier with time. Only with a mate. And Byleth was, unfortunately, rather single. 

The urge to roughly dominate was overpowering. Every time somebody walked by his room, he had to resist the urge to fuck or fight them - just by being able to smell another warm body separated by but a single door.

God forbid any other alphas get too close to his door right now - the violent fight that would ensue was something he wanted to avoid at all costs. So he just held his shirt over his nose and groaned miserably as he attempted to read. The lust was too overpowering to focus, but it was better than taking himself in hand and imagining he was penetrating a warm willing body only to finish in a mess and be just as restless as he had been when he began.

He was also, as usual, starving. He’d already devoured the snacks he kept in his room, gone several hours ago. Byleth had heavily debated making a quick dash to the kitchen to make off with as much as he could carry, but he had to admit it was just too much of a risk with this many people around - he would have to wait until after dark. Of course, Bylia would come looking for him eventually, and by then he could just have her bring him whatever he needed, but she didn’t know about his predicament yet so for at least the next several hours, he was on his own.

Byleth sighed and threw the book against the wall - wincing when it hit much harder than he had intended with a loud thump - and slumped back against his bed. He had been hard for so long it hurt, the blood stretching the skin uncomfortably tight across his shaft. Wincing as he palmed himself, he longed for relief that he knew would not come for several days until his rut was over.

With every touch, his mind began to wander… to the training session earlier. He was stuck on the image of Dimitri, pinned and helpless beneath him, eyes hazed over with desire. He would press his body down on Dimitri’s, engulfing the young man with his heat. He’d grind his erection against the hardness of Dimitri’s he had felt, relish the gasp of arousal he’d make in response. The blush that would paint his pale cheeks and the bridge of his nose. The sweat that would cling to the fair blond hairs at the back of his elegant neck. 

Just thinking about his neck made Byleth salivate - all slender and smooth, waiting to be marked by his teeth. Dangerously, dared to imagine him an omega - _ his _ omega - and his bite on the mating gland on his neck would claim him as his forever. He could just imagine the sound Dimitri would make as he bit down, claiming him as his forever.

Though he’d never seen Dimitri disrobed, he knew the broadness of his bare shoulders, the plane of his stomach, the way it would flex as he teased him - imagined his nipples, stiff pink ovals against hard pectoral muscles that spoke to the young royal’s determination to grow in strength. That precious earnestness and honorableness he wanted to protect, with his full being. Him calling out in his sweetest voice, yearning for Byleth, desiring no other.

Byleth growled, unable to help himself, fully jerking himself off now with furious movements, knowing when he came it would bring no relief. He couldn’t stop now - it was so clear in his mind, Dimitri was calling to him, begging for him to join them deep within his body. The warm wet heat of his walls would cling to him as if they never wanted him to withdraw, urging him to thrust as deep inside his omega’s body as possible. 

His Dimitri would raise his hips willingly, taking all of him to the hilt and then gasping for more - Byleth would give him anything, anything he wanted. 

It was a taboo pleasure, but it seized his mind and, admittedly, his heart and did not let go. Rut or no rut, he wanted Dimitri - his closest friend at the monastery, his trusted, honorable companion - wanted him more than a friend. More than an instructor. More than a commander in battle. 

Byleth wanted to make Dimitri groan and shudder beneath his hands, always protecting him, but overwhelming him with pleasure until he clung to him, entrusting the very depths of his heart and baring him his neck with pleading eyes. 

He would bite and suck the mating gland til it drew blood and knot inside his prince as he released the very essence of himself inexorably into Dimitri’s deepest place forging a bond that would never be broken.

The very thought of it filled him with so much pleasure he climaxed all over his sheets, the base of his shaft swelling up to knot in nothing but his hand.

As the pleasure faded, Byleth was left with a deep loneliness. Slumping back against the bed, he threw an arm over his face and let out a deep sigh. He stared at the ceiling wondering just how long he would have to endure this hell. And how he was going to face Dimitri now that he’d so inappropriately done everything to him and more in his mind. 

Somebody rapped on the door, making Byleth immediately bolt upright.

“Yeah, what?!” Only a particularly unaware beta would come near his room now - the cocktail of pheromones he was exuding took care of that. 

“It’s me, professor… I brought some food. May I come in or ah… should I simply leave it here for you and take my leave?” Dimitri’s voice - in contrast to Byleth’s recent fantasy, in it’s normal, measured tone. 

_ Food! _ It was almost funny how immediately his mood lifted. He really hated being hungry.

_ Dimitri! _ ...Dimitri? Byleth guiltily shoved his sheets to the side, creating a fold that hid his shameful exploitation of his imaginative ability. He then paused, staring at the door.

On the one hand, he really wanted that food, and a deep ache within his body relaxed in relief as if it could sense the object of his affections nearby. 

But on the other, he really shouldn’t see him. Not in this state. He was unstable, violent… there was no telling what he would do. At least Dimitri wasn’t an alpha - then he wouldn’t be able to stand any proximity at all, and he would rather die himself than hurt his precious… friend. Regardless of what ensued (Byleth briefly entertained the very dangerous thought of Dimitri in his bed for real) both of them were young adults, and his current… virile state coupled with his innate desire to _ dominate, impregnate _ spelled nothing but trouble. Even if he was a beta, and unable to be impregnated, it would be even worse because the beast within would just try harder, and thought Dimitri’s body could handle a lot, he loathed the thought of hurting him for his own sick pleasure.

“...Byleth?”

Byleth stared at the door longingly at the use of his name instead of his title - he was so lonely and horny he wanted to scream, and possibly find the Goddess or whoever was responsible for creating this situation and hurl _ them _ as far as he possibly could. Unfortunately, tenacious as she was, no Sothis nor any other divine being appeared in his consciousness or his room for him to do so.

Fuck everything. The urge within him to fling open the door and draw Dimitri inside to ravage him was unbearable.

Byleth pulled up his shorts and shot off the bed, footsteps thumping noisily as he streaked over to the door, nearly ripping the heavy oaken thing off it’s hinges with the force with which he flung it open.

The most delicious smell he’d ever smelled in his life engulfed his senses. Food, water, and, gazing up at him with concern in his sky blue eyes...

“Dimitri.”


	2. Of Body

**Summary for the Chapter:**

> *Tiffany Pollard Beyonce Face* An OMEGA??

“...Hello, Professor.” Dimitri seemed to be a loss for words as he took Byleth in, and raised the tray of food and drink as an offering instead, with a nervous smile.

Byleth took it automatically, movements jerky with his restraint. The pheromones in the air were intoxicating.

The food wasn’t the only thing that smelled absolutely unbearably delicious right now.

“Thanks for this. If I wasn’t already half outta my mind from the hormones, I was going crazy with hunger.” Byleth bit his lip. “I would invite you to come in... but I’m feral enough right now to bite. I wouldn’t have the restraint not to jump you.”

Dimitri nodded immediately. “I understand. It would be my honor to…” He trailed off, unable to make a choice of words. “...Help you, if you were willing to let me.”

“Uh...what? Really?” Byleth couldn’t believe what he was hearing. “I was joking. I don’t expect that from you.” As much as he would dream about and pine away after it, he had been prepared for a lonely rut.

The crestfallen look on Dimitri’s face immediately set his alpha hormones into a panic. 

“_ No! _ No I mean, I don’t expect that, but if you’re offering because you…” He almost didn’t dare say it. “...Like me? Then...”

Dimitri raised his eyes finally and fixed him with the sort of brave, determined look he often took to the battlefield. 

“I’ve always cared a great deal for you Profess-no, Byleth. More than a teacher. More than a friend or ally. You are my beloved - … my beloved. I’ve always been happiest by your side.”

“I- wow. Forgive me for not seeing that, Dimitri. I really wish I had, because the feeling is… definitely mutual.” Byleth grinned widely and made a motion with his head back at his room. “In that case, my room is all yours, hungry rutting alpha and all.”

He was shoveling spoonfuls of food into his mouth before he even sat down. The heavens had sent him a beautiful blond angel bearing food and, apparently, love, and he was damned if he wasn’t about to overwhelm his savior with gratitude in the form of what he planned to be the best lay of Dimitri’s life.

He was intrigued (and also amused, and pleased) to see Dimitri close and lock the door behind him. As Dimitri took a seat on the edge of his bed - with posture too polite for this situation, he thought, but befitting of the prince he was - Byleth paused his plate to mouth conveyor belt to take a long draw of water.

When he swallowed, Byleth raised the utensil to point at Dimitri. “Just so you know, soon as I fuel up, I intend to thoroughly ravish you.” It was his awkward way of telling him that while he didn’t know Dimitri’s second gender, he would bite and knot him if he stayed, and that now was the time to dip if he wasn’t okay with that.

“You needn’t worry about that, Professor.” 

Byleth raised an eyebrow inquisitively.

“You can imagine why, I’m sure, but I take suppressants to hide my identity as an omega.”

“An _ omega?!? _ ” Or that’s what Byleth meant to say, though it came out more like “_phfen homingah?!?_” around a mouth full of food.

Maybe he _ should _ reconsider how he felt about religion after all. In the space of fifteen minutes he’d been given pretty much everything he’d ever wanted in life.

Dimitri nodded and drew his shirt up with one hand, revealing -_ a very tempting strip of stomach, Byleth wanted to _\- his omega symbol.

Byleth shoveled one more bite into his mouth and then had to set the bowl down. He couldn’t continue, not with the image of _ his omega _ wet and needy for him, for his knot, taking it deep, _ his omega _ round with his child. _ His omega _in heat calling out for him. A small part of him was very relieved that they’d be able to make heirs. A much bigger -and louder- part of him wanted to start making them right away. 

Shoving the tray a bit harder on his desk than necessary, Byleth rose. There was no other word for the way he moved toward Dimitri other than _ stalk _, with full predatorial intent visible in not only his gait but the stiff flex of his muscles and the intense look in his eyes. 

Dimitri gave a shiver, and made an expression that gave Byleth no doubt he was much better than him at hiding just how much he wanted to be completely and utterly wrecked by his alpha. The hazy look from earlier on the training grounds was back, and Byleth intended to be just as rough as he pounded his knot into Dimitri’s ass as he had been with his sword. He knew he could take it.

Byleth made quick work of the thin tank top he wore and chucked it across the room. He appraised Dimitri’s still clothed, fidgety form.

“You don’t _ look _ like someone ready to get claimed and knotted. Or were you hoping I would pin you down and strip you?” 

Dimitri made a noise like he would’ve liked that very much. “Oh, of course, one moment!” He blurted out and began to take off his clothes. When he was down to only his boxers, Byleth’s hand shot out and stilled his before he could take them off.

“I figured the regalia was too complicated for me to remove anyways, and too expensive to replace, but I’m sure you’ll be able to live without this pair of boxers. Enjoy them while they last.” 

“Do whatever you wish to me or my clothing…”

Divulging himself of the rest of his own clothes, Byleth sat languidly against the head of his bed. Impatiently reaching both hands under Dimitri’s ass, Byleth lifted the other man into his lap. 

Trapping him in his embrace, he grasped a handful of the prince’s blond hair at the back of his head and thumbed his soft pink lips, giving an appreciative groan and how immediately they opened. He imagined the sight of his dick pistoning in and out between those pretty lips, sloppy with saliva, and those earnest blue eyes looking up at him with adoration. Byleth wanted that, incredibly badly, but that would have to wait for a time when he wouldn’t risk knotting in his mouth. He pressed his mouth to Dimitri’s in an aggressive kiss, invading the warm wet space with his tongue instead.

His omega liked that very much, the smell of arousal permeating the air. 

Running his hands up Dimitri’s muscled torso, he gave his large pecs an appreciative squeeze before circling the pink nipples with his thumbs and rubbing his erection against the hard line straining Dimitri’s boxers, the sounds of their kissing shamelessly filling the small room.

His omega rolled his hips hard back against his, jerking when he gave one stiff nipple a sharp pinch with a low drawn out moan. 

There was a tearing sound as Byleth ripped the thin fabric of Dimitri’s boxers, finally at his patience’s end. Luckily, his omega’s ass was already ready and dripping for him. Grasping Dimitri’s hips, he lifted his omega’s ass and rubbed his cock against Dimitri’s opening, breaking their kiss to bite and suck at Dimitri’s neck. 

He meant to enter him slowly and give him time to get adjusted to his girth, but he over-calculated the force necessary, and as slippery with slick as Dimitri’s ass already was, he hilted him in a single thrust. 

His omega shuddered and whined but began to shallowly raise himself up and down on his length, squeezing him with his tight walls.

“Am I- doing well for you Professor?”

“Gods yes, so obediently taking my cock up your ass.” At his words, pre-cum flowed from the tip of Dimitri’s dick and the tight ring of muscles squeezed down around him.

His omega seems to like to be praised.

Byleth grasped Dimitri’s ass and dragged his hips up and down, forcing him to take his dick harder. 

“Such a good omega, taking it all for me.” He murmured directly into Dimitri’s ear, punctuating with a bite. He rubbed a thumb into Dimitri’s pale stomach, imagining it bulging.

Dimitri’s muscles trembled as he rode him, shuddering in pleasure every time Byleth’s cock dragged against his prostate on the downstroke. Mouth open, panting hard, he was the picture of Byleth’s most erotic wet dreams. 

“P-Professor… your knot-” His face was a red, sweaty mess. “-I need it... please!”

“So good and eager.” Byleth thumbed Dimitri’s cheek and pushed a few blond locks out of his face. “You deserve a reward.”

He brought their lips back together in a deep kiss as he thrusted with abandon now, the base of his cock beginning to swell as his climax drew near. Dimitri just moaned through the kiss, insides squeezing and clenching. It felt way too good, and Byleth broke off the kiss to thrust as deeply into his omega as he could before cumming, knot swelling up to full size in Dimitri’s ass as he filled him up with his cum. 

Dimitri spasmed adorably on his knot with his own orgasm, coating his own stomach with ropes of spend. Spreading out his legs more comfortably, he drew his omega to his chest in a tight embrace. Dimitri submissively bared his neck, eyes pleading. He could never deny that earnest blue gaze. He raked his teeth down the column of Dimitri’s neck and paused for a moment before biting down hard on his mating gland, marking his omega as his own forever.

It filled him such a sweet rush of satisfaction and possessiveness. _ Mine, mine, mine _. He laced a hand through his omega’s soft hair, stroking the area by the base of his skull. Dimitri slumped contentedly against his chest in a way that tugged at his heart.

Byleth had a rough rut ahead of him but his days of horny-lonely pining after the prince he shouldn’t want were over.

**Notes for the Chapter:**

> Commissioned by Hannah Bell to release this next chapter! If anybody was feelin a bit *teased* then alas, be teased no more. ;) Dinner is served.

**Author's Note:**

> Second in an omegaverse series commissioned by Hannah Bell. Might end up with a second chapter if I have time, but its week 3 in colleg and I'm already drowning so... we'll see.  
She's like... top supporter of Two Souls at this point yall. I'm thankful and also shook :')
> 
> Anyways, Byleth wants to rough up Dimitri, and really, really hopes he's an omega. And that he likes him back.
> 
> (As said before, this is my custom m!byleth from Two Souls, in case you noticed the presence of a personality and were taken aback.)


End file.
